Mesogenic compounds comprising discotic and calamitic groups

ABSTRACT

The invention relates to novel calamitic mesogenic compounds which are especially suitable for use in birefringent films with negative optical dispersion, to novel liquid crystal (LC) formulations and polymer films comprising them, and to the use of the compounds, formulations and films in optical, electrooptical, electronic, semiconducting or luminescent components or devices.

FIELD OF THE INVENTION

The invention relates to novel mesogenic compounds comprising discoticand calamitic groups which are especially suitable for use inbirefringent films with negative optical dispersion, to novel liquidcrystal (LC) formulations and polymer films comprising them, and to theuse of the compounds, formulations and films in optical, electrooptical,electronic, semiconducting or luminescent components or devices.

BACKGROUND AND PRIOR ART

There is a need for anisotropic optical films that demonstrate negativeoptical retardation dispersion. For example, a quarter wave film madewith negative dispersion birefringent materials will be largelyachromatic. Devices such as reflective LCDs that utilise such a quarterwave film will have a dark state that is not coloured. Currently suchdevices have to use two retarder films to achieve this effect.

The dispersive power of such a negative dispersion birefringent film canbe defined in many ways, however one common way is to measure theoptical retardation at 450 nm and divide this by the optical retardationmeasured at 550 nm (R₄₅₀/R₅₅₀). If the on-axis retardation of a negativeretardation dispersion film at 550 nm is 137.5 nm and the R₄₅₀/R₅₅₀value is 0.82, then such a film will be a largely a quarter wave for allwavelengths of visible light and a liquid crystal display device (LCD)using this film as, for example, a circular polarizer would have asubstantially black appearance. On the other hand, a film made with anon axis of 137.5 nm which had normal positive dispersion (typicallyR₄₅₀/R₅₅₀=1.13) would only be a quarter wave for one wavelength (550nm), and an LCD device using this film as, for example, a circularpolarizer would have a purple appearance. Another way of representingthis information is to plot the change in birefringence as a function ofwavelength. FIG. 1 shows a typical birefringence against wavelength plotfor a polymerized film made from the commercially available reactivemesogen RM257 (Merck KgaA, Darmstadt, Germany). The R₄₅₀/R₅₅₀ for thiscompound is around 1.115.

In an anisotropic optical film formed by rod-shaped, opticallyanisotropic molecules, the origin of the retardation dispersion is dueto the fact that the two refractive indices n_(e), n_(o), of theanisotropic molecules (wherein n_(e) is the “extraordinary refractiveindex” in the direction parallel to the long molecular axis, and n_(o)is the “ordinary refractive index” in the directions perpendicular tothe long molecular axis) are changing with wavelength at differentrates, with n_(e) changing more rapidly than n_(o) towards the blue endof the visible wavelength spectrum. One way of preparing material withlow or negative retardation dispersion is to design molecules withincreased n_(o) dispersion and decreased n_(e) dispersion. This isschematically shown in FIG. 2. Such an approach has been demonstrated inprior art to give LC's with negative birefringence and positivedispersion as well as compounds with positive birefringence and negativedispersion.

If the compounds are polymerizable, or are mixed with a polymerizablehost material comprising for example polymerizable mesogenic compounds(also known as “reactive mesogens” or “RMs”), it is possible to prepareanisotropic optical polymer films with negative dispersion. This caneasily be carried out by in situ polymerization, e.g. by exposure toheat or UV radiation, of the polymerizable material when being uniformlyoriented in its mesophase, thereby permanently fixing themacroscopically uniform orientation. Suitable polymerization methods arewell-known to the person skilled in the art, and are described in theliterature.

Molecules that can be formed into anisotropic films that demonstrate theproperty of negative or reverse retardation dispersion have beendisclosed in prior art. For example, JP 2005-208146 A1 and WO2006/052001 A1 disclose polymerisable materials largely based oncompounds with a “cardo” core group.

Another class of compounds which is claimed to demonstrate negativebirefringence is described in U.S. Pat. No. 6,139,771. These compoundsgenerally consist of two rod-shaped mesogenic groups connected by anacetylenic or bis-acetylenic bridging group. The bridging group isconnected to the two rod-shaped groups using a benzene ring on therod-shaped part of the molecule, resulting in the bridge having an angleof approximately 60° to the rods.

U.S. Pat. No. 6,203,724 discloses molecules generally consisting of tworod-shaped mesogenic groups connected by a highly dispersive bridginggroup. The bridge is connected to the rod-shaped groups via a the axialposition of a cyclohexane ring.

WO 2005/085222 A1 and WO 2006/137599 A1 disclose molecules that have twolower refractive index parts connected by a higher refractive indexbridge part. The bridge is predominantly connected to the rods via afused five-membered heterocyclic ring.

In the compounds described in the above-mentioned documents, where therods are connected to a highly polarisable bridge, only a maximum of tworods is connected to the polarisable bridging group.

However, many of the materials disclosed in the literature havedrawbacks, like for example thermal properties that are not suitable forprocessing under standard industrial processes, limited solubility inthe solvents commonly used in standard industrial processes, or are notcompatible with host RM materials commonly used in standard industrialprocesses, or are too expensive to manufacture.

JP 2005-208414 A1 discloses molecules comprising rod-shaped groups thatare covalently bonded to a central discotic group. However in thecompounds specifically disclosed in that document, the rod-shapedmolecules are connected via an ester group to the discotic ring. Thepresence of such an ester group gives the rod freedom to rotate in atleast two directions relative to the ring. This decreases theprobability that the rods and disc will, on average, retain the correctorientation relative to each other, and thus prevents that the desiredoptical effect can be maximised.

This invention has the aim of providing improved compounds for use in LCformulations and polymer films having negative dispersion, which do nothave the drawbacks of the prior art materials.

In particular, there is a need for compounds that demonstrate reduced ornegative dispersion, and are also available at reduced cost and withimproved properties such as solubility and thermal properties.

Another aim of the invention is to extend the pool of materials andpolymer films having negative dispersion that are available to theexpert. Other aims are immediately evident to the expert from thefollowing description.

It has been found that these aims can be achieved by providingcompounds, materials and films as claimed in the present invention.

SUMMARY OF THE INVENTION

The invention relates to compounds of formula I

D[-(B)_(q)-M]_(z)  I

wherein

-   D is a discotic group, or forms a discotic group together with    (B)_(q),-   z is an integer from 3 to 10, very preferably 3, 4, 5 or 6,-   B is, in each occurrence independently of one another, a bivalent    group having high polarizability, preferably selected from the group    consisting of —C≡C—, —CY¹═CY²— and optionally substituted aromatic    or heteroaromatic groups,-   Y^(1,2) are independently of each other H, F, Cl, CN or R⁰,-   q is, in each occurrence independently of one another, 0 or an    integer from 1 to 10, preferably 0, 1, 2, 3, 4, 5 or 6,-   M is a group of formula II

wherein the individual radicals have, in case of multiple occurrenceindependently of one another, the following meanings

-   U¹ is selected from the group consisting of the following rings

-   -   including their mirror images, wherein the ring U¹ is bonded to        the group —(B)_(q)— via the axial bond, and one or two        non-adjacent CH₂ groups in these rings are optionally replaced        by O and/or S, and the ring U¹ is optionally substituted,

-   Q^(1,2) are independently of each other CH or SiH,

-   Q³ is C or Si,

-   A^(1,2) are independently of each other selected from non-aromatic,    aromatic or heteroaromatic carbocylic or heterocyclic groups, which    are optionally substituted, and wherein    -(A¹-Z¹)_(m)-U¹-(Z²-A²)_(n)-does not contain more aromatic groups    than non-aromatic groups and preferably does not contain more than    one aromatic group,

-   Z^(1,2) are independently of each other —O—, —S—, —CO—, —COO—,    —OCO—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—, —NR⁰—CO—NR⁰—, —OCH₂—, —CH₂O—,    —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —CH₂CH₂—, —(CH₂)₃—,    —(CH₂)₄—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—, —CH═CH—, —CY¹═CY²—, —CH═N—,    —N═CH—, —N═N—, —CH═CR⁰—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH—, CR⁰R⁰⁰ or    a single bond,

-   R⁰ and R⁰⁰ are independently of each other H or alkyl with 1 to 12    C-atoms,

-   m and n are independently of each other 0, 1, 2, 3 or 4, with m+n>0,

-   R¹⁻³ are independently of each other identical or different groups    selected from H, halogen, —CN, —NC, —NCO, —NCS, —OCN, —SCN,    —C(═O)NR⁰R⁰⁰, —C(═O)X⁰, —C(═O)R⁰, —NH₂, —NR⁰R⁰⁰—SH, —SR⁰, —SO₃H,    —SO₂R⁰, —OH, —NO₂, —CF₃, —SF₅, P-Sp-, optionally substituted silyl,    or carbyl or hydrocarbyl with 1 to 40 C atoms that is optionally    substituted and optionally comprises one or more hetero atoms, or    denote P or P-Sp-, or are substituted by P or P-Sp-,

-   P is a polymerizable group,

-   Sp is a spacer group or a single bond.

These compounds have the capability to induce or enhance a negativeoptical dispersion in liquid crystalline materials, and can be used forthe manufacture of polymer films exhibiting a negative dispersion.

The invention further relates to an LC formulation comprising one ormore compounds as described above and below.

The invention further relates to a polymerizable LC formulationcomprising one or more compounds as described above and below and one ormore further compounds, wherein at least one of the compounds ispolymerizable.

The invention further relates to a birefringent polymer obtainable bypolymerizing a compound or LC formulation as described above and below,preferably in its LC phase in an oriented state in form of a thin film.

The invention further relates to a birefringent polymer film withR₄₅₀/R₅₅₀<1, wherein R₄₅₀ is the optical on-axis retardation at awavelength of 450 nm and R₅₅₀ is the optical on-axis retardation at awavelength of 550 nm, said film being obtainable by polymerizing one ormore compounds or LC formulations as described above and below.

The invention further relates to the use of compounds, LC formulationsand polymers as described above and below in optical, electronic andelectrooptical components and devices, preferably in optical films,retarders or compensators having negative optical dispersion.

The invention further relates to an optical, electronic orelectrooptical component or device, comprising a compound, LCformulation or polymer as described above and below.

Said devices and components include, without limitation, electroopticaldisplays, LCDs, optical films, polarizers, compensators, beam splitters,reflective films, alignment layers, colour filters, holographicelements, hot stamping foils, coloured images, decorative or securitymarkings, LC pigments, adhesives, non-linear optic (NLO) devices,optical information storage devices, electronic devices, organicsemiconductors, organic field effect transistors (OFET), integratedcircuits (IC), thin film transistors (TFT), Radio FrequencyIdentification (RFID) tags, organic light emitting diodes (OLED),organic light emitting transistors (OLET), electroluminescent displays,organic photovoltaic (OPV) devices, organic solar cells (O-SC), organiclaser diodes (O-laser), organic integrated circuits (O-IC), lightingdevices, sensor devices, electrode materials, photoconductors,photodetectors, electrophotographic recording devices, capacitors,charge injection layers, Schottky diodes, planarising layers, antistaticfilms, conducting substrates, conducting patterns, photoconductors,electrophotographic applications, electrophotographic recording, organicmemory devices, biosensors, biochips, optoelectronic devices requiringsimilar phase shift at multiple wavelengths, combinedCD/DVD/HD-DVD/Blu-Rays, reading, writing re-writing data storagesystems, or cameras.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the birefringence versus wavelength plot for a polymerizedfilm made from a reactive mesogen of prior art.

FIG. 2 shows the refractive index versus wavelength plot of a modelledmolecule with low or negative retardation dispersion, showing increasedn_(o) dispersion and decreased n_(e) dispersion.

FIG. 3 a and FIG. 3 b show the birefringence versus wavelength plot fora compound with negative optical dispersion (3 a) and positive opticaldispersion (3 b), respectively.

FIG. 4 exemplarily and schematically illustrates the structure of acompound according to the present invention.

FIG. 5 exemplarily and schematically illustrates the structure of acompound according to prior art.

DEFINITIONS OF TERMS

The term “liquid crystal”, “mesomorphic compound, or “mesogeniccompound” (also shortly referred to as “mesogen”) means a compound thatunder suitable conditions of temperature, pressure and concentration canexist as a mesophase or in particular as a LC phase. Non-amphiphilicmesogenic compounds comprise for example one or more calamitic,banana-shaped or discotic mesogenic groups.

The term “calamitic” means a rod- or board/lath-shaped compound orgroup. The term “banana-shaped” means a bent group in which two, usuallycalamitic, mesogenic groups are linked through a semi-rigid group insuch a way as not to be collinear.

The term “discotic” means a disc- or sheet-shaped compound or group.

The term “mesogenic group” means a group with the ability to induceliquid crystal (LC) phase behaviour. Mesogenic groups, especially thoseof the non-amphiphilic type, are usually either calamitic or discotic.The compounds comprising mesogenic groups do not necessarily have toexhibit an LC phase themselves. It is also possible that they show LCphase behaviour only in mixtures with other compounds, or when themesogenic compounds or the mixtures thereof are polymerized. For thesake of simplicity, the term “liquid crystal” is used hereinafter forboth mesogenic and LC materials.

A calamitic mesogenic compound is usually comprising a calamitic, i.e.rod- or lath-shaped, mesogenic group consisting of one or more aromaticor alicyclic groups connected to each other directly or via linkagegroups, optionally comprising terminal groups attached to the short endsof the rod, and optionally comprising one or more lateral groupsattached to the long sides of the rod, wherein these terminal andlateral groups are usually selected e.g. from carbyl or hydrocarbylgroups, polar groups like halogen, nitro, hydroxy, etc., orpolymerizable groups.

A discotic mesogenic compound is usually comprising a discotic, i.e.relatively flat disc- or sheet-shaped mesogenic group consisting forexample of one or more condensed aromatic or alicyclic groups, like forexample triphenylene, and optionally comprising one or more terminalgroups that are attached to the mesogenic group and are selected fromthe terminal and lateral groups mentioned above.

For an overview of terms and definitions in connection with liquidcrystals and mesogens see Pure Appl. Chem. 73(5), 888 (2001) and C.Tschierske, G. Pelzl and S. Diele, Angew. Chem. 2004, 116, 6340-6368.

The term “reactive mesogen” (RM) means a polymerizable mesogenic orliquid crystal compound.

Polymerizable compounds with one polymerizable group are also referredto as “monoreactive” compounds, compounds with two polymerizable groupsas “direactive” compounds, and compounds with more than twopolymerizable groups as “multireactive” compounds. Compounds without apolymerizable group are also referred to as “non-reactive” compounds.

The term “spacer” or “spacer group”, also referred to as “Sp” below, isknown to the person skilled in the art and is described in theliterature, see, for example, Pure Appl. Chem. 73(5), 888 (2001) and C.Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.Unless stated otherwise, the term “spacer” or “spacer group” above andbelow denotes a flexible organic group, which in a polymerisablemesogenic compound (“RM”) connects the mesogenic group and thepolymerisable group(s).

The term “film” includes rigid or flexible, self-supporting orfree-standing films with mechanical stability, as well as coatings orlayers on a supporting substrate or between two substrates.

The term “pi-conjugated” means a group containing mainly C atoms withsp²-hybridisation, or optionally also sp-hybridisation, which may alsobe replaced by hetero atoms. In the simplest case this is for example agroup with alternating C—C single and double bonds, or triple bonds, butdoes also include groups like 1,3- or 1,4-phenylene. Also included inthis meaning are groups like for example aryl amines, aryl phosphinesand certain heterocycles (i.e. conjugation via N-, O-, P- or S-atoms).

The term “carbyl group” means any monovalent or multivalent organicradical moiety which comprises at least one carbon atom either withoutany non-carbon atoms (like for example —C≡C—), or optionally combinedwith at least one non-carbon atom such as N, O, S, P, Si, Se, As, Te orGe (for example carbonyl etc.). The term “hydrocarbyl group” denotes acarbyl group that does additionally contain one or more H atoms andoptionally contains one or more hetero atoms like for example N, O, S,P, Si, Se, As, Te or Ge. A carbyl or hydrocarbyl group comprising achain of 3 or more C atoms may also be linear, branched and/or cyclic,including spiro and/or fused rings.

On the molecular level, the birefringence of a liquid crystal depends onthe anisotropy of the polarizability (Δα=α_(II)−α_(⊥)). “Polarizability”means the ease with which the electron distribution in the atom ormolecule can be distorted. The polarizability increases with greaternumber of electrons and a more diffuse electron cloud. Thepolarizability can be calculated using a method described in eg Jap. J.Appl. Phys. 42, (2003) p 3463.

The “optical retardation” at a given wavelength R(λ) (in nm) of a layerof liquid crystalline or birefringent material is defined as the productof birefringence at that wavelength Δn(λ) and layer thickness d (in nm)according to the equation

R(λ)=Δn(λ)·d

The optical retardation R represents the difference in the optical pathlengths in nanometres traveled by S-polarised and P-polarised lightwhilst passing through the birefringent material. “On-axis” retardationmeans the retardation at normal incidence to the sample surface.

The term “negative (optical) dispersion” refers to a birefringent orliquid crystalline material or layer that displays reverse birefringencedispersion where the magnitude of the birefringence (Δn) increases withincreasing wavelength (λ). i.e |Δn(450)|<|Δn(550)|, orΔn(450)/Δn(550)<1, where Δn(450) and Δn(550) are the birefringence ofthe material measured at wavelengths of 450 nm and 550 nm respectively.In contrast, positive (optical) dispersion” means a material or layerhaving |Δn(450)|>|Δn(550)| or Δn(450)/Δn(550)>1. See also for example A.Uchiyama, T. Yatabe “Control of Wavelength Dispersion of Birefringencefor Oriented Copolycarbonate Films Containing Positive and NegativeBirefringent Units”. J. Appl. Phys. Vol. 42 pp 6941-6945 (2003).

This is shown schematically in FIG. 3 a.

Since the optical retardation at a given wavelength is defined as theproduct of birefringence and layer thickness as described above[R(λ)=Δn(λ)·d], the optical dispersion can be expressed either as the“birefringence dispersion” by the ratio Δn(450)/Δn(550), or as“retardation dispersion” by the ratio R(450)/R(550), wherein R(450) andR(550) are the retardation of the material measured at wavelengths of450 nm and 550 nm respectively. Since the layer thickness d does notchange with the wavelength, R(450)/R(550) is equal to Δn(450)/Δn(550).Thus, a material or layer with negative or reverse dispersion hasR(450)/R(550)<1 or |R(450)|<|R(550)|, and a material or layer withpositive or normal dispersion has R(450)/R(550)>1 or |R(450)|>|R(550)|.

In the present invention, unless stated otherwise “optical dispersion”means the retardation dispersion i.e. the ratio (R(450)/R(550).

The retardation (R(λ)) of a material can be measured using aspectroscopic ellipsometer, for example the M2000 spectroscopicellipsometer manufactured by J.A. Woollam Co., This instrument iscapable of measuring the optical retardance in nanometres of abirefringent sample e.g. Quartz over a range of wavelengths typically,370 nm to 2000 nm. From this data it is possible to calculate thedispersion (R(450)/R(550) or Δn(450)/Δn(550)) of a material.

A method for carrying out these measurements was presented at theNational Physics Laboratory (London, UK) by N. Singh in October 2006 andentitled “Spectroscopic Ellipsometry, Part 1—Theory and Fundamentals,Part 2—Practical Examples and Part 3—measurements”. In accordance withthe measurement procedures described Retardation Measurement (RetMeas)Manual (2002) and Guide to WVASE (2002) (Woollam Variable AngleSpectroscopic Ellipsometer) published by J. A. Woollam Co. Inc (Lincoln,Nebr., USA). Unless stated otherwise, this method is used to determinethe retardation of the materials, films and devices described in thisinvention.

DETAILED DESCRIPTION OF THE INVENTION

The prior art documents cited above demonstrate the general feasibilityof making negative dispersion films using polymerisable LCs. However, inaddition to the need for negative dispersion additives to demonstrategood solubility and thermal properties, it is also desired for theseadditives to show the desired optical effect with a minimumconcentration in the final LC mixture. Therefore it is desired to haveavailable compounds that impart an increased negative dispersion to theLC host mixture.

The inventors of the present invention have now found that this can beachieved by modifying the molecular structure of the negative dispersioncompounds. FIG. 4 shows a typical compound of prior art as disclosed forexample in U.S. Pat. No. 6,203,724, comprising a highly polarisablebridge, typically with an aromatic ring and two alkinyl groups, betweentwo rod shaped groups with low polarisability, which essentially consistof cyclohexane rings. It was found that the highly polarisable bridge isa key component that allows a film formed from such molecules todemonstrate negative birefringence dispersion. Restricting the freedomof the bridge to move relative to the rods should increase theeffectiveness of the negative dispersion additives. Furthermore, if thearomatic rings in the bridge have the freedom to rotate in and out ofthe plane, as schematically depicted by the arrow in FIG. 4, then thispart of the bridge can contribute to both n_(e) and n_(o). Thus,limiting the contribution of the bridge to n_(e) should increase theeffectiveness of the negative dispersion additive. With three or morerods around each central highly polarisable part of the molecule, anyaromatic rings will be predominantly orientated such as to maximise itscontribution to n_(o). In addition, increasing the number of rodsattached to the central aromatic ring should also help to increase theLC properties of the molecule.

To summarise, there are the following reasons why it is expected thatthe structurally modified compounds according to the present inventionwill show improved performance over the prior art compounds:

-   1. Restricting the freedom of the bridge to move relative to the    rods will increase the effectiveness of the negative dispersion    additives. Therefore, linking the two moieties via a suitably    substituted axial cyclohexane linking group should achieve this    effect better than linking it via an ester group.-   2. Limiting the contribution the bridge makes to n_(e) will increase    the effectiveness of the negative dispersion dopant. Further    restricting the freedom of any aromatic rings to rotate out of plane    by predominantly anchoring the orientation with three rather than    two rods should maximise its contribution to n_(o) whilst minimising    its contribution to n_(e).-   3. Increasing the number of rods attached to a central ring should    help to increase the liquid crystalline properties of the molecule.

The above modifications were realised by providing compounds of formulaI according to the present invention. These compounds do generallyconsist of two distinct molecular parts as exemplarily and schematicallyshown in FIG. 5: A central discotic core (1), for example a ringstructure or a group comprising two or more rings, surrounded by threeor more rod shaped groups (2). The molecular geometry of the systemincreases the probability that the plane of the ring will be heldlargely perpendicular to the long axis of the rod-shaped molecular part.The rod-shaped groups (2) do preferably consist predominantly of groupswith low polarisability such as cyclohexane rings. At the end of therods polymerisable groups (3) can be attached. The distribution of thepolymerisable groups is random and they can also be all at the same sideof the molecule. The number of polymerisable groups can be as low asone. The central part of the molecule (1) predominantly consists ofhighly polarisable groups like for example aromatic rings. The rods (2)are connected via a lateral group to the core (1). The lateral groupconnecting the rod (2) to the core (1) is chosen so that it restrictsthe freedom of the rod to revolve relative to the core. Overall, themolecule will have low birefringence in long axis of the molecule andhigh birefringence in the lateral part of the molecule (=the discoticcore).

In the compounds of formula I, the discotic group D preferably denotesbenzene, which is preferably tri-, tetra or hexavalent, or triphenylene,which is preferably hexavalent. Very preferably the discotic group D isselected from the group consisting of the following formulae:

The group (B)_(q) having high polarizability is preferably consistingmainly, very preferably exclusively, of one or more subgroups B, whichare selected from pi-conjugated linear groups, aromatic andheteroaromatic groups.

Preferably the group (B)_(q) consists, very preferably exclusively, ofone or more subgroups B selected from groups having a bonding angle of120° or more, preferably in the range of 180°. Suitable and preferredsubgroups B include, without limitation, groups comprising sp-hybridisedC-atoms, like —C≡C—, or divalent aromatic groups connected to theirneighboured groups in para-position, like e.g. 1,4-phenylene,naphthalene-2,6-diyl, indane-2,6-diyl orthieno[3,2-b]thiophene-2,5-diyl.

In the groups (B)_(q) q may also be 0, so that (B)_(q) is a single bondand the corresponding group M is attached directly to the discoticgroup.

Preferably, however, the compounds of formula I comprise at least one,more preferably at least two groups (B)_(q) wherein q is different from0. Further preferred are compounds of formula I wherein each q isdifferent from 0.

The group (B)_(q) is preferably a linear group consisting of subgroups Bhaving bonding angles of approx. 180°, and is linked to the calamiticcompound via an sp³-hybridised C-atom (i.e. with a bonding angle ofapprox. 109°). Thereby it is possible to achieve a structure where thelong axis of the calamitic mesogenic groups M are largely perpendicularto the plane of the ring of the discotic group D.

The group (B)_(q), which essentially consists of subgroups B withpi-conjugation, has a high polarizability and a high refractive index.If the mesogenic groups M are selected to have a low polarizability anda low refractive index, then as a result the compounds show, dependingon their exact structure, either positive birefringence and negativedispersion, as schematically depicted in FIG. 3 a, or negativebirefringence with positive dispersion, as schematically depicted inFIG. 3 b.

As a reference, normal calamitic materials have positive birefringenceand positive dispersion. It is desirable to have materials where themagnitude of Δn decreases at shorter wavelength, and compounds with bothpositive dispersion and negative birefringence can be mixed with a hostmaterial to give a mixture which possesses a range of dispersion(depending on the concentration of the dopant and host) varying frompositive birefringence with positive dispersion through to positivebirefringence with negative dispersion.

The subgroups B are preferably selected from groups having a bondingangle of 120° or more, preferably in the range of 180°. Very preferredare —C≡C— groups or divalent aromatic groups connected to their adjacentgroups in para-position, like e.g. 1,4-phenylene, naphthalene-2,6-diyl,indane-2,6-diyl or thieno[3,2-b]thiophene-2,5-diyl.

Further possible subgroups B include —CH═CH—, —CY¹═CY²—, and —CH═CR⁰—wherein Y¹, Y², R⁰ have the meanings given above.

Preferably the bridging group —(B)_(q)— in formula I comprises one ormore groups selected from the group consisting of —C≡C—, optionallysubstituted 1,4-phenylene and optionally substituted9H-fluorene-2,7-diyl. The subgroups, or B in formula I, are preferablyselected from the group consisting of —C≡C—, optionally substituted1,4-phenylene and optionally substituted 9H-fluorene-2,7-diyl, whereinin the fluorene group the H-atom in 9-position is optionally replaced bya carbyl or hydrocarbyl group.

Very preferably the bridging group —(B)_(q)— in formula I is selectedfrom the group consisting of —C≡C—, —C≡C—C≡C—, —C≡C—C≡C—C≡C—,—C≡C—C≡C—C≡C—C≡C—,

wherein r is 0, 1, 2, 3 or 4 and L has the meaning as described below.

The rings U¹ in formula II are preferably selected from

wherein R³ is as defined in formula I.

The groups M are preferably calamitic mesogenic groups, very preferablyrod-shaped mesogenic groups.

Preferably the groups M comprise one or more groups selected fromaromatic or heteroaromatic rings, and non-aromatic, e.g. fully orpartially saturated, carbocyclic or heterocyclic groups, said groupsbeing linked to each other either directly or via linkage groups.

Preferably the groups M are selected such that they exhibit a lowpolarizability. This can be achieved e.g. by using mesogenic groups thatare preferably comprising mainly non-aromatic, most preferably fullysaturated, carbocyclic or heterocyclic groups which are connecteddirectly or via linkage groups, wherein “mainly” means that eachmesogenic group comprises more saturated rings than unsaturated oraromatic rings, and very preferably does not comprise more than oneunsaturated or aromatic ring.

Especially preferred are compounds of formula I, wherein all groups Mare identical.

Further preferred are compounds of formula I, wherein in one or moregroups M, very preferably in each group M, the subgroups -(Z¹-A¹)_(m)-R¹and -(Z²-A²)_(n)-R² are different from each other.

Further preferred are compounds of formula I, wherein at least one ofthe groups A¹ or A² linked to the central ring U¹ is cyclohexylene, andvery preferably said group A¹ or A² is directly attached to U¹, i.e. thecorresponding group Z¹ or Z² between U¹ and said group A¹ or A² is asingle bond.

The aromatic groups, like A^(1,2), may be mononuclear, i.e. having onlyone aromatic ring (like for example phenyl or phenylene), orpolynuclear, i.e. having two or more fused rings (like for examplenapthyl or naphthylene). Especially preferred are mono-, bi- ortricyclic aromatic or heteroaromatic groups with up to 25 C atoms thatmay also comprise fused rings and are optionally substituted.

Preferred aromatic groups include, without limitation, benzene,biphenylene, triphenylene, [1,1′:3′,1″]terphenyl-2′-ylene, naphthalene,anthracene, binaphthylene, phenanthrene, pyrene, dihydropyrene,chrysene, perylene, tetracene, pentacene, benzpyrene, fluorene, indene,indenofluorene, spirobifluorene, etc.

Preferred heteroaromatic groups include, without limitation, 5-memberedrings like pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole,tetrazole, furan, thiophene, selenophene, oxazole, isoxazole,1,2-thiazole, 1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole,1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole,1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-memberedrings like pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine,1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine,1,2,3,5-tetrazine, and fused systems like carbazole, indole, isoindole,indolizine, indazole, benzimidazole, benzotriazole, purine,naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazin-imidazole,quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole,phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran,dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline,benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine,phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine,quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline,phenanthridine, phenanthroline, thieno[2,3b]thiophene,thieno[3,2b]thiophene, dithienothiophene, dithienopyridine,isobenzothiophene, dibenzothiophene, benzothiadiazothiophene, orcombinations thereof.

The non-aromatic carbocyclic and heterocyclic groups, like A¹⁻⁴, includethose which are saturated (also referred to as “fully saturated”), i.e.they do only contain C-atoms or hetero atoms connected by single bonds,and those which are unsaturated (also referred to as “partiallysaturated”), i.e. they also comprise C-atoms or hetero atoms connectedby double bonds. The non-aromatic rings may also comprise one or morehetero atoms, preferably selected from Si, O, N and S.

The non-aromatic carbocyclic and heterocyclic groups may be mononuclear,i.e. having only one ring (like for example cyclohexane), orpolynuclear, i.e. having two or more fused rings (like for exampledecahydronaphthalene or bicyclooctane). Especially preferred are fullysaturated groups. Further preferred are mono-, bi- or tricyclicnon-aromatic groups with up to 25 C atoms that optionally comprise fusedrings and are optionally substituted. Very preferred are 5-, 6-, 7- or8-membered carbocyclic rings wherein one or more C-atoms are optionallyreplaced by Si and/or one or more CH groups are optionally replaced by Nand/or one or more non-adjacent CH₂ groups are optionally replaced by—O— and/or —S—, all of which are optionally substituted.

Preferred non-aromatic rings include, without limitation, 5-memberedrings like cyclopentane, tetrahydrofuran, tetrahydrothiofuran,pyrrolidine, 6-membered rings like cyclohexane, silinane, cyclohexene,tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane, 1,3-dithiane,piperidine, 7-membered rings like cycloheptane, and fused systems liketetrahydronaphthalene, decahydronaphthalene, indane,bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl,spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methano-indan-2,5-diyl, orcombinations thereof.

Preferably the non-aromatic and aromatic rings, like A^(1,2), areselected from trans-1,4-cyclohexylene and 1,4-phenylene that isoptionally substituted with one or more groups L.

Very preferably the mesogenic groups M comprise not more than onearomatic ring.

Very preferred are compounds of formula I and II wherein m and n are 0,1 or 2, in particular wherein one of m and n is 1 and the other is 0 or1.

In the calamitic compounds of the present invention, the linkage groupsconnecting the aromatic and non-aromatic cyclic groups in the mesogenicgroups, like Z^(1,2), are preferably selected from —O—, —S—, —CO—,—COO—, —OCO—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—, —NR⁰—CO—NR⁰—, —OCH₂—, —CH₂O—,—SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —CH₂CH₂—, —(CH₂)₃—,—(CH₂)₄—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—, —CH═CH—, —CY¹═CY²—, —CH═N—,—N═CH—, —N═N—, —CH═CR⁰—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH—, CR⁰R⁰⁰ or asingle bond, very preferably from —COO—, —OCO— and a single bond.

In the calamitic compounds of the present invention, the substituents onthe groups B, U¹, A^(1,2) and R^(1,3), also referred to as “L”, arepreferably selected from P-Sp-, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS,—OCN, —SCN, —C(═O)NR⁰R⁰⁰, —C(═O)X, —C(═O)OR⁰, —C(═O)R⁰, —NR⁰R⁰⁰, —OH,—SF₅, optionally substituted silyl, aryl or heteroaryl with 1 to 12,preferably 1 to 6 C atoms, and straight chain or branched alkyl, alkoxy,alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxywith 1 to 12, preferably 1 to 6 C atoms, wherein one or more H atoms areoptionally replaced by F or Cl, wherein R⁰ and R⁰⁰ are as defined informula I and X is halogen.

Preferred substituents L are selected from F, Cl, ON, NO₂ or straightchain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl,alkylcarbonlyoxy or alkoxycarbonyloxy with 1 to 12 C atoms, wherein thealkyl groups are optionally perfluorinated, or P-Sp-.

Very preferred substituents are selected from F, Cl, CN, NO₂, CH₃, C₂H₅,C(CH₃)₃, CH(CH₃)₂, CH₂CH(CH₃)C₂H₅, OCH₃, OC₂H₅, COCH₃, COC₂H₅, COOCH₃,COOC₂H₅, CF₃, OCF₃, OCHF₂, OC₂F₅ or P-Sp-, in particular F, Cl, CN, CH₃,C₂H₅, C(CH₃)₃, CH(CH₃)₂, OCH₃, COCH₃ or OCF₃, most preferably F, Cl,CH₃, C(CH₃)₃, OCH₃ or COCH₃, or P-Sp-.

is preferably or

with L having each independently one of the meanings given above.

The carbyl and hydrocarbyl groups R¹⁻³ are preferably selected fromstraight-chain, branched or cyclic alkyl with 1 to 40, preferably 1 to25 C-atoms, which is unsubstituted, mono- or polysubstituted by F, Cl,Br, I or CN, and wherein one or more non-adjacent CH₂ groups areoptionally replaced, in each case independently from one another, by—O—, —S—, —NH—, —NR⁰—, —SiR⁰R⁰⁰—, —CO—, —COO—, —OCO—, —O—CO—O—, —S—CO—,—CO—S—, —SO₂—, —CO—NR⁰—, —NR⁰—CO—, —NR⁰—CO—NR⁰⁰—, —CY¹≡CY²— or —C≡C— insuch a manner that O and/or S atoms are not linked directly to oneanother, wherein Y¹ and Y² are independently of each other H, F, Cl orCN, and R⁰ and R⁰⁰ are independently of each other H or an optionallysubstituted aliphatic or aromatic hydrocarbon with 1 to 20 C atoms.

Very preferably R¹ and R² are selected from, C₁-C₂₀-alkyl,C₁-C₂₀-oxaalkyl, C₁-C₂₀-alkoxy, C₂-C₂₀-alkenyl, C₂-C₂₀-alkynyl,C₁-C₂₀-thioalkyl, C₁-C₂₀-silyl, C₁-C₂₀-ester, C₁-C₂₀-amino,C₁-C₂₀-fluoroalkyl.

R³ is preferably H or methyl.

An alkyl or alkoxy radical, i.e. where the terminal CH₂ group isreplaced by —O—, can be straight-chain or branched. It is preferablystraight-chain, has 2, 3, 4, 5, 6, 7 or 8 carbon atoms and accordinglyis preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl,ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, or octoxy,furthermore methyl, nonyl, decyl, undecyl, dodecyl, tridecyl,tetradecyl, pentadecyl, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy ortetradecoxy, for example.

Oxaalkyl, i.e. where one CH₂ group is replaced by —O—, is preferablystraight-chain 2-oxapropyl (=methoxymethyl), 2- (=ethoxymethyl) or3-oxabutyl (=2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-, 3-, 4-, or5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-,7-, 8- or 9-oxadecyl, for example.

An alkyl group wherein one or more CH₂ groups are replaced by —CH═CH—can be straight-chain or branched. It is preferably straight-chain, has2 to 10 C atoms and accordingly is preferably vinyl, prop-1-, orprop-2-enyl, but-1-, 2- or but-3-enyl, pent-1-, 2-, 3- or pent-4-enyl,hex-1-, 2-, 3-, 4- or hex-5-enyl, hept-1-, 2-, 3-, 4-, 5- orhept-6-enyl, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-, 3-,4-, 5-, 6-, 7- or non-8-enyl, dec-1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- ordec-9-enyl.

Especially preferred alkenyl groups are C₂-C₇-1E-alkenyl,C₄-C₇-3E-alkenyl, C₅-C₇-1E-alkenyl, C₆-C₇-5-alkenyl and C₇₋₆-alkenyl, inparticular C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl and C₅-C₇-4-alkenyl.Examples for particularly preferred alkenyl groups are vinyl,1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl,3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl,4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groupshaving up to 5 C atoms are generally preferred.

In an alkyl group wherein one CH₂ group is replaced by —O— and one by—CO—, these radicals are preferably neighboured. Accordingly theseradicals together form a carbonyloxy group —CO—O— or an oxycarbonylgroup —O—CO—. Preferably this group is straight-chain and has 2 to 6 Catoms. It is accordingly preferably acetyloxy, propionyloxy, butyryloxy,pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl,butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl,2-propionyloxy-ethyl, 2-butyryloxyethyl, 3-acetyloxypropyl,3-propionyloxypropyl, 4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl,propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl,ethoxy-carbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl,2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl,2-(propoxycarbonyl)ethyl, 3-(methoxycarbonyl)propyl,3-(ethoxycarbonyl)propyl, 4-(methoxycarbonyl)-butyl.

An alkyl group wherein two or more CH₂ groups are replaced by —O— and/or—COO— can be straight-chain or branched. It is preferably straight-chainand has 3 to 12 C atoms. Accordingly it is preferablybis-carboxy-methyl, 2,2-bis-carboxy-ethyl, 3,3-bis-carboxy-propyl,4,4-bis-carboxy-butyl, 5,5-bis-carboxy-pentyl, 6,6-bis-carboxy-hexyl,7,7-bis-carboxy-heptyl, 8,8-bis-carboxy-octyl, 9,9-bis-carboxy-nonyl,10,10-bis-carboxy-decyl, bis-(methoxycarbonyl)-methyl,2,2-bis-(methoxycarbonyl)-ethyl, 3,3-bis-(methoxycarbonyl)-propyl,4,4-bis-(methoxycarbonyl)-butyl, 5,5-bis-(methoxycarbonyl)-pentyl,6,6-bis-(methoxycarbonyl)-hexyl, 7,7-bis-(methoxycarbonyl)-heptyl,8,8-bis-(methoxycarbonyl)-octyl, bis-(ethoxycarbonyl)-methyl,2,2-bis-(ethoxycarbonyl)-ethyl, 3,3-bis-(ethoxycarbonyl)-propyl,4,4-bis-(ethoxycarbonyl)-butyl, 5,5-bis-(ethoxycarbonyl)-hexyl.

An alkyl or alkenyl group that is monosubstituted by CN or CF₃ ispreferably straight-chain. The substitution by CN or CF₃ can be in anydesired position.

An alkyl or alkenyl group that is at least monosubstituted by halogen ispreferably straight-chain. Halogen is preferably F or Cl, in case ofmultiple substitution preferably F. The resulting groups include alsoperfluorinated groups. In case of monosubstitution the F or Clsubstituent can be in any desired position, but is preferably inω-position. Examples for especially preferred straight-chain groups witha terminal F substituent are fluoromethyl, 2-fluoroethyl,3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and7-fluoroheptyl. Other positions of F are, however, not excluded.

R⁰ and R⁰⁰ are preferably selected from H, straight-chain or branchedalkyl with 1 to 12 C atoms. —CY¹═CY²— is preferably —CH═CH—, —CF═CF— or—CH═C(CN)—.

Halogen is F, Cl, Br or I, preferably F or Cl.

R¹⁻³ can be an achiral or a chiral group. Particularly preferred chiralgroups are 2-butyl (=1-methylpropyl), 2-methylbutyl, 2-methylpentyl,3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, in particular2-methylbutyl, 2-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy,2-ethylhexoxy, 1-methylhexoxy, 2-octyloxy, 2-oxa-3-methylbutyl,3-oxa-4-methylpentyl, 4-methylhexyl, 2-hexyl, 2-octyl, 2-nonyl, 2-decyl,2-dodecyl, 6-methoxyoctoxy, 6-methyloctoxy, 6-methyloctanoyloxy,5-methylheptyloxycarbonyl, 2-methylbutyryloxy, 3-methylvaleroyloxy,4-methylhexanoyloxy, 2-chlorpropionyloxy, 2-chloro-3-methylbutyryloxy,2-chloro-4-methylvaleryloxy, 2-chloro-3-methylvaleryloxy,2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl, 1-methoxypropyl-2-oxy,1-ethoxypropyl-2-oxy, 1-propoxypropyl-2-oxy, 1-butoxypropyl-2-oxy,2-fluorooctyloxy, 2-fluorodecyloxy, 1,1,1-trifluoro-2-octyloxy,1,1,1-trifluoro-2-octyl, 2-fluoromethyloctyloxy for example. Verypreferred are 2-hexyl, 2-octyl, 2-octyloxy, 1,1,1-trifluoro-2-hexyl,1,1,1-trifluoro-2-octyl and 1,1,1-trifluoro-2-octyloxy.

Preferred achiral branched groups are isopropyl, isobutyl(=methylpropyl), isopentyl (=3-methylbutyl), isopropoxy,2-methyl-propoxy and 3-methylbutoxy.

The polymerizable group P is a group that is capable of participating ina polymerization reaction, like radical or ionic chain polymerization,polyaddition or polycondensation, or capable of being grafted, forexample by condensation or addition, to a polymer backbone in a polymeranalogous reaction. Especially preferred are polymerizable groups forchain polymerization reactions, like radical, cationic or anionicpolymerization. Very preferred are polymerizable groups comprising a C—Cdouble or triple bond, and polymerizable groups capable ofpolymerization by a ring-opening reaction, like oxetanes or epoxides.

Suitable and preferred polymerizable groups include, without limitation,CH₂═CW¹—COO—, CH₂═CW¹—CO—,

CH₂═CW²—(O)_(k1)—, CH₃—CH═CH—O—, (CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—,(CH₂═CH)₂CH—O—, (CH₂═CH—CH₂)₂N—, (CH₂═CH—CH₂)₂N—CO—, HO—CW²W³—,HS—CW²W³, HW²N—, HO—CW²W³—NH—, CH₂═CW¹—CO—NH—,CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—, CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—,Phe-CH═CH—, HOOC—, OCN—, and W⁴W⁵W⁶Si—, with W¹ being H, F, Cl, CN, CF₃,phenyl or alkyl with 1 to 5 C-atoms, in particular H, C₁ or CH₃, W² andW³ being independently of each other H or alkyl with 1 to 5 C-atoms, inparticular H, methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ beingindependently of each other Cl, oxaalkyl or oxacarbonylalkyl with 1 to 5C-atoms, W⁷ and W⁸ being independently of each other H, Cl or alkyl with1 to 5 C-atoms, Phe being 1,4-phenylene that is optionally substituted,preferably by one or more groups L as defined above (except for themeaning P-Sp-), and k₁ and k₂ being independently of each other 0 or 1.

Very preferred polymerizable groups are selected from CH₂═CW¹—COO—,CH₂═CW¹—CO—,

(CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—, (CH₂═CH)₂CH—O—, (CH₂═CH—CH₂)₂N—,(CH₂═CH—CH₂)₂N—CO—, HO—CW²W³—, HS—CW²W³—, HW²N—, HO—CW²W³—NH—,CH₂═CW¹—CO—NH—, CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—,CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—, Phe-CH═CH—, HOOC—, OCN—, and W⁴W⁵W⁶Si—,with W¹ being H, F, Cl, CN, CF₃, phenyl or alkyl with 1 to 5 C-atoms, inparticular H, F, C₁ or CH₃, W² and W³ being independently of each otherH or alkyl with 1 to 5 C-atoms, in particular H, methyl, ethyl orn-propyl, W⁴, W⁵ and W⁶ being independently of each other Cl, oxaalkylor oxacarbonylalkyl with 1 to 5 C-atoms, W⁷ and W⁸ being independentlyof each other H, Cl or alkyl with 1 to 5 C-atoms, Phe being1,4-phenylene that is optionally substituted preferably by one or moregroups L as defined above (except for the meaning P-Sp-), and k₁ and k₂being independently of each other 0 or 1.

Most preferred polymerizable groups are selected from CH₂═CH—COO—,CH₂═C(CH₃)—COO—, CH₂═CF—COO—, (CH₂═CH)₂CH—OCO—, (CH₂═CH)₂CH—O—,

Polymerization can be carried out according to methods that are known tothe ordinary expert and described in the literature, for example in D.J. Broer; G. Challa; G. N. Mol, Macromol. Chem, 1991, 192, 59.

The spacer group Sp is preferably selected of formula Sp′-X′, such thatP-Sp- is P-Sp′-X′—, wherein

-   Sp′ is alkylene with 1 to 20 C atoms, preferably 1 to 12 C-atoms,    which is optionally mono- or polysubstituted by F, Cl, Br, I or CN,    and wherein one or more non-adjacent CH₂ groups are optionally    replaced, in each case independently from one another, by —O—, —S—,    —NH—, —NR⁰—, —SiR⁰R⁰⁰—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—,    —NR⁰—CO—O—, —O—CO—NR⁰—, —NR⁰—CO—NR⁰—, —CH═CH— or —C≡C— in such a    manner that O and/or S atoms are not linked directly to one another,-   X′ is —O—, —S—, —CO—, —COO—, —OCO—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—,    —NR⁰—CO—NR⁰—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—,    —CF₂S—, —SCF₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—, —CH═N—, —N═CH—, —N═N—,    —CH═CR⁰—, —CY¹≡CY²—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH— or a single    bond,-   R⁰ and R⁰⁰ are independently of each other H or alkyl with 1 to 12    C-atoms, and-   Y¹ and Y² are independently of each other H, F, Cl or CN.-   X′ is preferably —O—, —S—CO—, —COO—, —OCO—, —O—COO—, —CO—NR⁰—,    —NR⁰—CO—, —NR⁰—CO—NR⁰— or a single bond.

Typical groups Sp′ are, for example, —(CH₂)_(p1)—,—(CH₂CH₂O)_(q1)—CH₂CH₂—, —CH₂CH₂—S—CH₂CH₂— or —CH₂CH₂—NH—CH₂CH₂— or—(SiR⁰R⁰⁰—O)_(p1)—, with p1 being an integer from 2 to 12, q1 being aninteger from 1 to 3 and R⁰ and R⁰⁰ having the meanings given above.

Preferred groups Sp′ are ethylene, propylene, butylene, pentylene,hexylene, heptylene, octylene, nonylene, decylene, undecylene,dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxy-butylene,ethylene-thioethylene, ethylene-N-methyl-iminoethylene,1-methylalkylene, ethenylene, propenylene and butenylene for example.Further preferred are chiral spacer groups.

Further preferred are compounds wherein the polymerizable group isdirectly attached to the mesogenic group without a spacer group Sp.

In case of compounds with two or more groups P-Sp-, the polymerizablegroups P and the spacer groups Sp can be identical or different.

In another preferred embodiment the calamitic compounds comprise one ormore terminal groups R^(1,2) or substituents L or R³ that aresubstituted by two or more polymerizable groups P or P-Sp-(multifunctional polymerizable groups). Suitable multifunctionalpolymerizable groups of this type are disclosed for example in U.S. Pat.No. 7,060,200 B1 oder US 2006/0172090 A1. Very preferred are compoundscomprising one or more multifunctional polymerizable groups selectedfrom the following formulae:

-X-alkyl-CHP¹—CH₂—CH₂P²  P1

-X′-alkyl-C(CH₂P¹)(CH₂P²)—CH₂P³  P2

-X′-alkyl-CHP¹CHP²—CH₂P³  P3

-X′-alkyl-C(CH₂P¹)(CH₂P²)—C_(aa)H_(2aa+1)  P4

-X′-alkyl-CHP¹—CH₂P²  P5

-X′-alkyl-CHP¹P²  P5

-X′-alkyl-CP¹P²—C_(aa)H_(2aa+1)  P6

-X′-alkyl-C(CH₂P¹)(CH₂P²)—CH₂OCH₂—C(CH₂P³)(CH₂P⁴)CH₂P⁵  P7

-X′-alkyl-CH((CH₂)_(aa)P¹)((CH₂)_(bb)P²)  P8

-X′-alkyl-CHP¹CHP²—C_(aa)H_(2aa+1)  P9

wherein

-   alkyl is straight-chain or branched alkylene having 1 to 12 C-atoms    which is unsubstituted, mono- or polysubstituted by F, Cl, Br, I or    CN, and wherein one or more non-adjacent CH₂ groups are optionally    replaced, in each case independently from one another, by —O—, —S—,    —NH—, —NR⁰—, —SiR⁰R⁰⁰—, —CO—, —COO—, —OCO—, —O—CO—O—, —S—CO—,    —CO—S—, —SO₂—, —CO—NR⁰—, —NR⁰—CO—, —NR⁰—CO—NR⁰⁰—, —CY¹═CY²— or —C≡C—    in such a manner that O and/or S atoms are not linked directly to    one another, with R⁰ and R⁰⁰ having the meanings given above, or    denotes a single bond,-   aa and bb are independently of each other 0, 1, 2, 3, 4, 5 or 6,-   X′ is as defined above, and-   P¹⁻⁵ independently of each other have one of the meanings given for    P above.

Preferred compounds of formula I are selected from the group consistingof the following subformulae:

wherein M is as defined above and below, and the phenylene rings areoptionally substituted by one or more groups L as defined above.

The groups M are preferably selected from the group consisting of thefollowing subformulae:

wherein R″ and R′″ have independently of each other one of the meaningsof R¹ given above, and Z has in each occurrence independently of oneanother one of the meanings of Z¹ given above. Preferably one or more ofR″ and R′″, very preferably both groups R″ and/or both groups R′″,denote P- or P-Sp-. Z is preferably —COO—, —OCO— or a single bond. Thephenyl rings are optionally substituted by one or more, preferably oneor two groups L as defined above.

P-Sp- in these preferred compounds is preferably P-Sp′-X′, with X′preferably being —O—, —COO— or —OCOO—. Z is preferably —COO—, —OCO— or asingle bond.

The compounds of formula I can be synthesized according to or in analogyto methods which are known per se and which are described in theliterature and in standard works of organic chemistry such as, forexample, Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag,Stuttgart. Especially suitable methods are disclosed in U.S. Pat. No.6,203,724. Further suitable methods of synthesis are also describedbelow and in the examples.

The compounds of formula I can be generally synthesized by initiallyreacting a suitably substituted acetylene, e.g.(trimethylsilyl)acetylene, with a suitable cyclohexanone in the presenceof butyllithium, as described e.g. in ACS Symposium Series (2001), 798(Anisotropic Organic Materials), 195-205. Esterification of theresulting tertiary alcohol with a suitable carboxylic acid yields anester product. The axial acetylenic substituent is then coupled to areactive discotic derivative of the formula D(B-G)_(z), wherein D, B andZ have the meanings of formula I and G is a suitable reactive group orleaving group, e.g. bromine or iodine, via a palladium catalyzedcoupling reaction in analogy to the method as described e.g. in either JOrg. Chem. 1997, 62, 7471, or Tetrahedron Lett. 1993, 6403.

The method for making the key intermediates is exemplarily shown belowin Scheme 1

Intermediate 1 is prepared as shown in Scheme 1 above. Compound 1.3 isprepared in two steps by reacting the ketone 1.1 with trimethylacetylenein the presence of butyl lithium, and then removing the TMS group usingpotassium hydroxide. Compound 1.3 is then reacted with a suitablecarboxylic acid in the presence of DCC and catalytic amount of DMAP.

Typical examples of Intermediate 1 are shown below:

Intermediate 1 (for example compound 1.4 or 1.5) is then coupled with ahalogenated discotic group preferably in a Sonogashira reaction. Forexample, intermediate 1 can be coupled with 1,3,5-triiodo- or1,3,5-tribromobenzene or other discotic groups as mentioned below, inthe presence of a suitable catalyst, for example a Pd(II) catalyst likePd(PPh3)₂Cl₂ and in the presence of a base, like for exampletriethylamine.

The methods of preparing a compound of formula I as described above andbelow are another aspect of the invention. Especially preferred is amethod comprising the following steps:

-   a) reacting a suitably substituted acetylene with an optionally    substituted cyclohexanone in the presence of butyllithium,-   b) separating the isomers thereby formed,-   c) esterification the tertiary alcohol of the isolated isomer of    step b) with a suitable aromatic or aliphatic carboxylic acid,-   d) coupling the resulting compound via its axial acetylenic    substituent to an aromatic ring.

The discotic groups D1-D6 are well-known in prior art. The discoticgroups D7-D11 can be prepared according to or in analogy to the methodsdescribed in the references cited below:

D7: See US 2008/087879A1, which describes the synthesis oftetrabromocoronenes like 1,4,7,10-tetrabromocoronene.

D8: The synthesis of the isomers2,8,15-Triiodo-5,6,11,12,17,18-hexaazatrinaphthylene and2,8,14-Triiodo-5,6,11,12,17,18-hexaazatrinaphthylene as shown below isdescribed in WO 2005/123737 A2.

D9: The synthesis of 2,7,12-Tribromotruxene is described in A. W. Amicket al., J. Org. Chem. 2007, 72(9), 3412-3418, and B. Gomez-Lor et al.,Eur. J. Org. Chem. 2001, 11, 2107-2114.

2,8,14-Triiodo-5,6,11,12,17,18-hexaazatrinaphthylene

2,8,15-Triiodo-5,6,11,12,17,18-hexaazatrinaphthylene

D10: See US 2005/048313 A1, which describes the synthesis of3,6,9,12-tetrahalogenatedanthanthrene.

D11: See “Columnar mesophase formation of cyclohexa-m-phenylene-basedmacrocycles”, W. Pisula et al. “Chemistry—An Asian Journal” (2007),2(1), 51-56. Publisher: Wiley-VCH Verlag GmbH & Co. KGaA, CODEN: CAAJBI,ISSN: 1861-4728; CAN147:395541, AN 2007:94977, which describes thesynthesis of 5,5′,5″,5′″,5″″,5″″′-Hexaiodohexa-m-phenylene.

The methods of preparing a compound of formula I as described above andbelow, the novel intermediates used therein and obtained thereby, andtheir use for preparing compounds of formula I, are further aspects ofthe invention.

Preferably the birefringent polymer film according to the presentinvention is prepared by polymerizing an LC formulation comprising oneor more compounds of formula I, hereinafter referred to as “guestcomponent” or “guest compound”, and further comprising an LC material,which may be a single compound or a mixture of compounds, hereinafterreferred to as “host component” or “host mixture”, preferably apolymerizable LC host mixture having a nematic phase. The terms “guest”and “host” do not exclude the possibility that the amount of the guestcomponent in the final LC mixture is >50% by weight, and the amount ofthe host component in the final LC mixture is <50% by weight.

The birefringent polymer film according to the present inventionpreferably has positive birefringence and negative (or “reverse”)dispersion.

The host component preferably has positive birefringence and positive(or “normal”) dispersion.

The guest component preferably has:

-   (1) Negative birefringence at 550 nm and normal (positive)    birefringence dispersion or-   (2) Positive birefringence at 550 nm and reverse (negative)    birefringence dispersion. In this case Δn(450)/Δn(550) can be    negative if the guest component has a negative birefringence at 450    nm.

Another aspect of the invention is a polymerizable formulation,preferably a polymerizable LC formulation, comprising one or more guestcompounds as described above and below, and one or more additionalcompounds, which are preferably mesogenic or liquid crystalline and/orpolymerizable. Very preferably the LC formulation comprises one or moreadditional compounds selected from reactive mesogens (RMs), mostpreferably selected from mono- and direactive RMs. These additionalcompounds constitute the polymerizable LC host component.

Preferably the polymer films according to the present invention arecrosslinked, and the polymerizable guest compounds and/or thepolymerizable host components comprise at least one compound with two ormore polymerizable groups (di- or multireactive).

The concentration of the guest compound(s) of the present invention inthe polymerizable LC formulation (including both the guest and hostcomponent) is preferably from 5 to 90 wt. %, very preferably from 30 to70 wt. %.

The additional RMs of the polymerizable LC host formulation can beprepared by methods which are known per se and which are described instandard works of organic chemistry like for example Houben-Weyl,Methoden der organischen Chemie, Thieme-Verlag, Stuttgart. Suitable RMsare disclosed for example in WO 93/22397, EP 0 261 712, DE 195 04 224,WO 95/22586, WO 97/00600, U.S. Pat. No. 5,518,652, U.S. Pat. No.5,750,051, U.S. Pat. No. 5,770,107 and U.S. Pat. No. 6,514,578. Examplesof particularly suitable and preferred RMs are shown in the followinglist.

wherein

-   P⁰ is, in case of multiple occurrence independently of one another,    a polymerizable group, preferably an acryl, methacryl, oxetane,    epoxy, vinyl, vinyloxy, propenyl ether or styrene group,-   A⁰ and B⁰ are, in case of multiple occurrence independently of one    another, 1,4-phenylene that is optionally substituted with 1, 2, 3    or 4 groups L, or trans-1,4-cyclohexylene,-   Z⁰ is, in case of multiple occurrence independently of one another,    —COO—, —OCO—, —CH₂CH₂—, —C≡C—, —CH═CH—, —CH═CH—COO—, —OCO—CH═CH— or    a single bond,-   R⁰ is alkyl, alkoxy, thioalkyl, alkylcarbonyl, alkoxycarbonyl,    alkylcarbonyloxy or alkoxycarbonyloxy with 1 or more, preferably 1    to 15 C atoms which is optionally fluorinated, or is Y⁰ or    P—(CH₂)_(y)—(O)_(z)—,-   X⁰ is —O—, —S—, —CO—, —COO—, —OCO—, —O—COO—, —CO—NR⁰¹—, —NR⁰¹—CO—,    —NR⁰¹—CO—NR⁰¹—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O —, —OCF₂—,    —CF₂S—, —SCF₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—, —CH═N—, —N═CH—, —N═N—,    —CH═CR⁰¹—, —CF═CF—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH— or a single bond-   Y⁰ is F, Cl, CN, NO₂, OCH₃, OCN, SCN, SF₅, optionally fluorinated    alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy    with 1 to 4 C atoms, or mono- oligo- or polyfluorinated alkyl or    alkoxy with 1 to 4 C atoms,-   R^(01,02) are independently of each other H, R⁰ or Y⁰,-   R* is a chiral alkyl or alkoxy group with 4 or more, preferably 4 to    12 C atoms, like 2-methylbutyl, 2-methyloctyl, 2-methylbutoxy or    2-methyloctoxy,-   Ch is a chiral group selected from cholesteryl, estradiol, or    terpenoid radicals like menthyl or citronellyl,-   L is, in case of multiple occurrence independently of one another,    H, F, Cl, CN or optionally halogenated alkyl, alkoxy, alkylcarbonyl,    alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy with 1 to 5 C    atoms,-   r is 0, 1, 2, 3 or 4,-   t is, in case of multiple occurrence independently of one another,    0, 1, 2 or 3,-   u and v are independently of each other 0, 1 or 2,-   w is 0 or 1,-   x and y are independently of each other 0 or identical or different    integers from 1 to 12,-   z is 0 or 1, with z being 0 if the adjacent x or y is 0,    and wherein the benzene and napthalene rings can additionally be    substituted with one or more identical or different groups L.

Especially preferably the polymerizable LC host component contains onlyachiral compounds and no chiral compounds.

Further preferably the polymerizable LC host component comprises one ormore compounds selected from formula MR3, MR4, MR7, MR8, MR9, MR10,MR18, MR27, DR6, DR7, DR8, DR9 and DR10, furthermore DR1 and DR5.Further preferably the polymerizable LC host component comprises one ormore compounds selected from the following formulae:

wherein P⁰, R⁰, x, y, and z are as defined above.

Further preferably the polymerizable LC host component comprises one ormore compounds selected from the following formulae:

Preferably the polymerizable compounds of the polymerizable LC hostcomponent are selected from compounds, very preferably mono- ordireactive RMs, having low birefringence.

Especially preferred is a polymerizable host component having anabsolute value of the birefringence from 0.01 to 0.2, very preferablyfrom 0.04 to 0.16.

The general preparation of polymer LC films according to this inventionis known to the ordinary expert and described in the literature, forexample in D. J. Broer; G. Challa; G. N. Mol, Macromol. Chem, 1991, 192,59. Typically a polymerizable LC material (i.e. a compound or a mixtureor formulation) is coated or otherwise applied onto a substrate where italigns into uniform orientation, and polymerized in situ in its LC phaseat a selected temperature for example by exposure to heat or actinicradiation, preferably by photo-polymerization, very preferably byUV-photopolymerization, to fix the alignment of the LC molecules. Ifnecessary, uniform alignment can promoted by additional means likeshearing or annealing the LC material, surface treatment of thesubstrate, or adding surfactants to the LC material.

As substrate for example glass or quartz sheets or plastic films can beused. It is also possible to put a second substrate on top of the coatedmaterial prior to and/or during and/or after polymerization. Thesubstrates can be removed after polymerization or not. When using twosubstrates in case of curing by actinic radiation, at least onesubstrate has to be transmissive for the actinic radiation used for thepolymerization. Isotropic or birefringent substrates can be used. Incase the substrate is not removed from the polymerized film afterpolymerization, preferably isotropic substrates are used.

Suitable and preferred plastic substrates are for example films ofpolyester such as polyethyleneterephthalate (PET) orpolyethylene-naphthalate (PEN), polyvinylalcohol (PVA), polycarbonate(PC) or triacetylcellulose (TAC), very preferably PET or TAC films. Asbirefringent substrates for example uniaxially stretched plastics filmcan be used. PET films are commercially available for example fromDuPont Teijin Films under the trade name Melinex®.

The polymerizable material can be applied onto the substrate byconventional coating techniques like spin-coating or blade coating. Itcan also be applied to the substrate by conventional printing techniqueswhich are known to the expert, like for example screen printing, offsetprinting, reel-to-reel printing, letter press printing, gravureprinting, rotogravure printing, flexographic printing, intaglioprinting, pad printing, heat-seal printing, ink-jet printing or printingby means of a stamp or printing plate.

It is also possible to dissolve the polymerizable material in a suitablesolvent. This solution is then coated or printed onto the substrate, forexample by spin-coating or printing or other known techniques, and thesolvent is evaporated off before polymerization. In many cases it issuitable to heat the mixture in order to facilitate the evaporation ofthe solvent. As solvents for example standard organic solvents can beused. The solvents can be selected for example from ketones such asacetone, methyl ethyl ketone, methyl propyl ketone or cyclohexanone;acetates such as methyl, ethyl or butyl acetate or methyl acetoacetate;alcohols such as methanol, ethanol or isopropyl alcohol; aromaticsolvents such as toluene or xylene; halogenated hydrocarbons such as di-or trichloromethane; glycols or their esters such as PGMEA (propylglycol monomethyl ether acetate), γ-butyrolactone, and the like. It isalso possible to use binary, ternary or higher mixtures of the abovesolvents.

Initial alignment (e.g. planar alignment) of the polymerizable LCmaterial can be achieved for example by rubbing treatment of thesubstrate, by shearing the material during or after coating, byannealing the material before polymerization, by application of analignment layer, by applying a magnetic or electric field to the coatedmaterial, or by the addition of surface-active compounds to thematerial. Reviews of alignment techniques are given for example by I.Sage in “Thermotropic Liquid Crystals”, edited by G. W. Gray, John Wiley& Sons, 1987, pages 75-77; and by T. Uchida and H. Seki in “LiquidCrystals—Applications and Uses Vol. 3”, edited by B. Bahadur, WorldScientific Publishing, Singapore 1992, pages 1-63. A review of alignmentmaterials and techniques is given by J. Cognard, Mol. Cryst. Liq. Cryst.78, Supplement 1 (1981), pages 1-77.

Especially preferred is a polymerizable material comprising one or moresurfactants that promote a specific surface alignment of the LCmolecules. Suitable surfactants are described for example in J. Cognard,Mol. Cryst. Liq. Cryst. 78, Supplement 1, 1-77 (1981). Preferredaligning agents for planar alignment are for example non-ionicsurfactants, preferably fluorocarbon surfactants such as thecommercially available Fluorad FC-171® (from 3M Co.) or Zonyl FSN® (fromDuPont), multiblock surfactants as described in GB 2 383 040 orpolymerizable surfactants as described in EP 1 256 617.

It is also possible to apply an alignment layer onto the substrate andprovide the polymerizable material onto this alignment layer. Suitablealignment layers are known in the art, like for example rubbed polyimideor alignment layers prepared by photoalignment as described in U.S. Pat.No. 5,602,661, U.S. Pat. No. 5,389,698 or U.S. Pat. No. 6,717,644.

It is also possible to induce or improve alignment by annealing thepolymerizable LC material at elevated temperature, preferably at itspolymerization temperature, prior to polymerization.

Polymerization is achieved for example by exposing the polymerizablematerial to heat or actinic radiation. Actinic radiation meansirradiation with light, like UV light, IR light or visible light,irradiation with X-rays or gamma rays or irradiation with high energyparticles, such as ions or electrons. Preferably polymerization iscarried out by UV irradiation. As a source for actinic radiation forexample a single UV lamp or a set of UV lamps can be used. When using ahigh lamp power the curing time can be reduced. Another possible sourcefor actinic radiation is a laser, like for example a UV, IR or visiblelaser.

Polymerization is preferably carried out in the presence of an initiatorabsorbing at the wavelength of the actinic radiation. For this purposethe polymerizable LC material preferably comprises one or moreinitiators, preferably in a concentration from 0.01 to 10%, verypreferably from 0.05 to 5%. For example, when polymerizing by means ofUV light, a photoinitiator can be used that decomposes under UVirradiation to produce free radicals or ions that start thepolymerization reaction. For polymerizing acrylate or methacrylategroups preferably a radical photoinitiator is used. For polymerizingvinyl, epoxide or oxetane groups preferably a cationic photoinitiator isused. It is also possible to use a thermal polymerization initiator thatdecomposes when heated to produce free radicals or ions that start thepolymerization. Typical radical photoinitiators are for example thecommercially available Irgacure® or Darocure® (Ciba Geigy AG, Basel,Switzerland). A typical cationic photoinitiator is for example UVI 6974(Union Carbide).

The polymerizable material may also comprise one or more stabilizers orinhibitors to prevent undesired spontaneous polymerization, like forexample the commercially available Irganox® (Ciba Geigy AG, Basel,Switzerland).

The curing time depends, inter alia, on the reactivity of thepolymerizable material, the thickness of the coated layer, the type ofpolymerization initiator and the power of the UV lamp. The curing timeis preferably ≦5 minutes, very preferably ≦3 minutes, most preferably ≦1minute. For mass production short curing times of ≦30 seconds arepreferred.

Preferably polymerization is carried out in an inert gas atmosphere likenitrogen or argon.

The polymerizable material may also comprise one or more dyes having anabsorption maximum adjusted to the wavelength of the radiation used forpolymerization, in particular UV dyes like e.g. 4,4″-azoxy anisole orTinuvin® dyes (from Ciba AG, Basel, Switzerland).

In another preferred embodiment the polymerizable material comprises oneor more monoreactive polymerizable non-mesogenic compounds, preferablyin an amount of 0 to 50%, very preferably 0 to 20%. Typical examples arealkylacrylates or alkylmethacrylates.

In another preferred embodiment the polymerizable material comprises oneor more di- or multireactive polymerizable non-mesogenic compounds,preferably in an amount of 0 to 50%, very preferably 0 to 20%,alternatively or in addition to the di- or multireactive polymerizablemesogenic compounds. Typical examples of direactive non-mesogeniccompounds are alkyldiacrylates or alkyldimethacrylates with alkyl groupsof 1 to 20 C atoms. Typical examples of multireactive non-mesogeniccompounds are trimethylpropanetrimethacrylate orpentaerythritoltetraacrylate.

It is also possible to add one or more chain transfer agents to thepolymerizable material in order to modify the physical properties of thepolymer film. Especially preferred are thiol compounds, for examplemonofunctional thiols like dodecane thiol or multifunctional thiols liketrimethylpropane tri(3-mercaptopropionate). Very preferred are mesogenicor LC thiols as disclosed for example in WO 96/12209, WO 96/25470 orU.S. Pat. No. 6,420,001. By using chain transfer agents the length ofthe free polymer chains and/or the length of the polymer chains betweentwo crosslinks in the polymer film can be controlled. When the amount ofthe chain transfer agent is increased, the polymer chain length in thepolymer film decreases.

The polymerizable material may also comprise a polymeric binder or oneor more monomers capable of forming a polymeric binder, and/or one ormore dispersion auxiliaries. Suitable binders and dispersion auxiliariesare disclosed for example in WO 96/02597. Preferably, however, thepolymerizable material does not contain a binder or dispersionauxiliary.

The polymerizable material can additionally comprise one or moreadditives like for example catalysts, sensitizers, stabilizers,inhibitors, chain-transfer agents, co-reacting monomers, surface-activecompounds, lubricating agents, wetting agents, dispersing agents,hydrophobing agents, adhesive agents, flow improvers, defoaming agents,deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes,pigments or nanoparticles.

The thickness of a polymer film according to the present invention ispreferably from 0.3 to 5 microns, very preferably from 0.5 to 3 microns,most preferably from 0.7 to 1.5 microns. For use as alignment layer,thin films with a thickness of 0.05 to 1, preferably 0.1 to 0.4 micronsare preferred.

The polymer films and materials of the present invention can be used asretardation or compensation film for example in LCDs to improve thecontrast and brightness at large viewing angles and reduce thechromaticity. It can be used outside the switchable LC cell of the LCDor between the substrates, usually glass substrates, forming theswitchable LC cell and containing the switchable LC medium (incellapplication).

The polymer film and materials of the present invention can be used inconventional LC displays, for example displays with vertical alignmentlike the DAP (deformation of aligned phases), ECB (electricallycontrolled birefringence), CSH (colour super homeotropic), VA(vertically aligned), VAN or VAC (vertically aligned nematic orcholesteric), MVA (multi-domain vertically aligned), PVA (patternedvertically aligned) or PSVA (polymer stabilised vertically aligned)mode; displays with bend or hybrid alignment like the OCB (opticallycompensated bend cell or optically compensated birefringence), R-OCB(reflective OCB), HAN (hybrid aligned nematic) or pi-cell (π-cell) mode;displays with twisted alignment like the TN (twisted nematic), HTN(highly twisted nematic), STN (super twisted nematic), AMD-TN (activematrix driven TN) mode; displays of the IPS (in plane switching) mode,or displays with switching in an optically isotropic phase.

The layers, films and materials of the present invention can be used forvarious types of optical films, preferably selected from opticallyuniaxial films (A-plate, C-plate, negative C-plate, O-plate), twistedoptical retarders, like for example twisted quarter wave foils (QWF),achromatic retarders, achromatic QWFs or half wave foils (HWF), andoptically biaxial films. The LC phase structure in the layers andmaterials can be selected from cholesteric, smectic, nematic and bluephases. The alignment of the LC material in the layer can be selectedfrom homeotropic, splayed, tilted, planar and blue-phase alignment. Thelayers can be uniformly oriented or exhibit a pattern of differentorientations.

The films can be used as optical compensation film for viewing angleenhancement of LCD's or as a component in a brightness enhancementfilms, furthermore as an achromatic element in reflective ortransflective LCD's. Further preferred applications and devices include

-   -   retarding components in optoelectronic devices requiring similar        phase shift at multiple wavelengths, such as combined        CD/DVD/HD-DVD/Blu-Ray, including reading, writing re-writing        data storage systems    -   achromatic retarders for optical devices such as cameras    -   achromatic retarders for displays including OLED and LCD's.

The following examples are intended to explain the invention withoutrestricting it. The methods, structures and properties describedhereinafter can also be applied or transferred to materials that areclaimed in this invention but not explicitly described in the foregoingspecification or in the examples.

Above and below, percentages are percent by weight. All temperatures aregiven in degrees Celsius. m.p. denotes melting point, cl.p. denotesclearing point, T_(g) denotes glass transition temperature. Furthermore,C=crystalline state, N=nematic phase, S=smectic phase and I=isotropicphase. The data between these symbols represent the transitiontemperatures. Δn denotes the optical anisotropy (Δn=n_(e)−n_(o), wheren_(o) denotes the refractive index parallel to the longitudinalmolecular axes and n_(e) denotes the refractive index perpendicularthereto), measured at 589 nm and 20° C. The optical and electroopticaldata are measured at 20° C., unless expressly stated otherwise.

In the description and claims of this specification, unless statedotherwise the retardation and dispersion are determined by the methodsas described above.

Unless stated otherwise, the percentages of components of apolymerizable mixture as given above and below refer to the total amountof solids in the mixture polymerizable mixture, i.e. not includingsolvents.

Example 1

Compound 1, wherein R is n-propyl, is prepared as described below.Intermediate 1.4 is prepared by the method described in Scheme 1, and isthen reacted with 1,3,5-triiodobenzene under Sonogashira conditions togive 1.

The Synthesis of 1.3 has been Described in the Literature, See e.g. US1999-0452166. Trans-4′-propyl-[1,1′-Bicyclohexyl]-4-one (1.1) iscommercially available.Trans,trans)-4′-propyl-4-[2-(trimethylsilyl)ethynyl]-[1,1′-Bicyclohexyl]-4-ol(1.2) was prepared by reacting 1.1 with trimethylsilylacetylene andbutyl lithium. The reaction produces two isomers and the trans-transisomer is isolated by column chromatography.(trans,trans)-4-ethynyl-4′-propyl-[1,1′-Bicyclohexyl]-4-ol (1.3) isprepared by reacting 1.2 with potassium hydroxide in methanol.

Synthesis of 1.4

To a stirring dichloromethane solution of the tertiary alcohol—compound3, was added a premixed solution of Trifluoroacetic anhydride and4-[6-(3-chloropropionyloxy)hexyloxy]benzoic acid in dichloromethane.After stirring overnight at 25° C. the reaction mixture was diluted withwater and the organic layer separated. After extracting the aqueouslayer with DCM, the combined organics were washed with sodium hydrogencarbonate solution and water until neutral pH. The material was purifiedusing silica gel column chromatography, eluting with 20% DCM in petrol40-60° C., affording an off-white solid (NMR shows expected signals, 98%yield).

Synthesis of 1

A round bottom flask was charged with the ester-compound 1.4,1,3,5-triiodobenzene, CuI, Pd(PPh₄)₂Cl₂ and triethylamine intetrahydrofuran and treated with sonication before being heated withstirring at 50° C. under nitrogen for 72 hours. After cooling, thereaction mixture was acidified by adding dilute HCl, the organic layerwas separated and washed with water. The organic layer was dried usingsodium sulphate, and concentrated to give a brown oil. The oil waspurified using silica gel column chromatography eluting with ethylacetate-petrol 40-60° C. (1:10). The fractions containing the productwere collected to give a dark brown solid which was redissolved indichloromethane and added to stirring acetonitrile pre-cooled to −20° C.The dark brown precipitate was collected and recrystallised from ethylacetate/denatured ethanol to give a yellow solid (96.1% by HPLC, 22%yield)

Example 2

1,3,5-tris[(4-iodophenyl)ethynyl]benzene is prepared via the methoddescribed in Nature (1999), 398, 796-799. Compound 1.4 of Example 1 isreacted with 1,3,5-tris[(4-iodophenyl)ethynyl]benzene under Sonogashiraconditions to give compound 2 as shown below.

1. Compounds of formula ID[-(B)_(q)-M]_(z)  I wherein D is a discotic group, or forms a discoticgroup together with (B)_(q), z is an integer from 3 to 10, B is, in eachoccurrence independently of one another, a bivalent group having highpolarizability, preferably selected from the group consisting of —C≡C—,—CY¹═CY²— and optionally substituted aromatic or heteroaromatic groups,Y^(1,2) are independently of each other H, F, Cl, CN or R⁰, q is, ineach occurrence independently of one another, 0 or an integer from 1 to10, M is a group of formula II

wherein the individual radicals have, in case of multiple occurrenceindependently of one another, the following meanings U¹ is selected fromthe group consisting of the following rings

including their mirror images, wherein the ring U¹ is bonded to thegroup —(B)_(q)— via the axial bond, and one or two non-adjacent CH₂groups in these rings are optionally replaced by O and/or S, and thering U¹ is optionally substituted, Q^(1,2) are independently of eachother CH or SiH, Q³ is C or Si, A^(1,2) are independently of each otherselected from non-aromatic, aromatic or heteroaromatic carbocylic orheterocyclic groups, which are optionally substituted, and wherein-(A¹-Z¹)_(m)-U¹-(Z²-A²)_(n)-does not contain more aromatic groups thannon-aromatic groups and preferably does not contain more than onearomatic group, Z^(1,2) are independently of each other —O—, —S—, —CO—,—COO—, —OCO—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—, —NR⁰—CO—NR⁰—, —OCH₂—, —CH₂O—,—SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —CH₂CH₂—, —(CH₂)₃—,—(CH₂)₄—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—, —CH═CH—, —CY¹═CY²—, —CH═N—,—N═CH—, —N═N—, —CH═CR⁰—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH—, CR⁰R⁰⁰ or asingle bond, R⁰ and R⁰⁰ are independently of each other H or alkyl with1 to 12 C-atoms, m and n are independently of each other 0, 1, 2, 3 or4, with m+n>0, R¹⁻³ are independently of each other identical ordifferent groups selected from H, halogen, —CN, —NC, —NCO, —NCS, —OCN,—SCN, —C(═O)NR⁰R⁰⁰, —C(═O)X⁰, —C(═O)R⁰, —NH₂, —NR⁰R⁰⁰, —SH, —SR⁰, —SO₃H,—SO₂R⁰, —OH, —NO₂, —CF₃, —SF₅, P-Sp-, optionally substituted silyl, orcarbyl or hydrocarbyl with 1 to 40 C atoms that is optionallysubstituted and optionally comprises one or more hetero atoms, or denoteP or P-Sp-, or are substituted by P or P-Sp-, P is a polymerizablegroup, Sp is a spacer group or a single bond.
 2. Compounds according toclaim 1, characterized in that D is selected from the group consistingof the following subformulae:


3. Compounds according to claim 1, characterized in that —(B)_(q)— isselected from the group consisting of —C≡C—, —C≡C—C≡C—, —C≡C—C≡C—C≡C—,—C≡C—C≡C—C≡C—C≡C—,

wherein r is 0, 1, 2, 3 or 4 and L is selected from P-Sp-, F, Cl, Br, I,—CN, —NO₂, —NCO, —NCS, —OCN, —SCN, —C(═O)NR⁰R⁰⁰, —C(═O)X, —C(═O)OR⁰,—C(═O)R⁰, —NR⁰R⁰⁰, —OH, —SF₅, optionally substituted silyl, aryl with 1to 12 C atoms, and straight chain or branched alkyl, alkoxy,alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxywith 1 to 12 C atoms, wherein one or more H atoms are optionallyreplaced by F or Cl, wherein R⁰ and R⁰⁰ are as defined in claim 1 and Xis halogen.
 4. Compounds according to claim 1, characterized in thatthey are selected from the group consisting of the followingsubformulae:

wherein M is as defined in claim 1, and the phenylene rings areoptionally substituted by one or more groups L wherein L is selectedfrom P-Sp-, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN,—C(═O)NR⁰R⁰⁰, —C(═O)X, —C(═O)OR⁰, —C(═O)R⁰, —NR⁰R⁰⁰, —OH, —SF₅,optionally substituted silyl, aryl with 1 to 12 C atoms, and straightchain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl,alkylcarbonyloxy or alkoxycarbonyloxy with 1 to 12 C atoms, wherein oneor more H atoms are optionally replaced by F or Cl, wherein R⁰ and R⁰⁰are as defined in claim 1 and X is halogen.
 5. Compounds according toclaim 1, characterized in that the groups M are preferably selected fromthe group consisting of the following subformulae:

wherein R″ and R′″ have independently of each other one of the meaningsof R¹ of claim 1, and Z has in each occurrence independently of oneanother one of the meanings of Z¹ of claim
 1. 6. Compounds according toclaim 1, characterized in that the rings U¹ in formula II are selectedfrom

wherein R³ is as defined in formula I.
 7. Polymerizable LC formulationcomprising one or more compounds according to claim 1, and one or morefurther compounds, wherein at least one of the compounds ispolymerizable.
 8. Birefringent polymer film obtainable by polymerizing acompound or LC formulation according to claim 1 in its LC phase in anoriented state in form of a thin film.
 9. Birefringent polymer filmaccording to claim 8, characterized in that it has R₄₅₀/R₅₅₀<1, whereinR₄₅₀ is the optical on-axis retardation at a wavelength of 450 nm andR₅₅₀ is the optical on-axis retardation at a wavelength of 550 nm.
 10. Amethod of using a compound of claim 1 which comprises preparing opticalfilms, retarders or compensators having negative optical dispersion withsaid compounds for optical, electronic and electrooptical components anddevices.
 11. Optical, electronic or electrooptical component or device,comprising a compound, LC formulation or polymer film according toclaim
 1. 12. Device or component according to claim 11, characterized inthat is is selected from electrooptical displays, LCDs, optical films,polarizers, compensators, beam splitters, reflective films, alignmentlayers, colour filters, holographic elements, hot stamping foils,coloured images, decorative or security markings, LC pigments,adhesives, non-linear optic (NLO) devices, optical information storagedevices, electronic devices, organic semiconductors, organic fieldeffect transistors (OFET), integrated circuits (IC), thin filmtransistors (TFT), Radio Frequency Identification (RFID) tags, organiclight emitting diodes (OLED), organic light emitting transistors (OLET),electroluminescent displays, organic photovoltaic (OPV) devices, organicsolar cells (O-SC), organic laser diodes (O-laser), organic integratedcircuits (O-IC), lighting devices, sensor devices, electrode materials,photoconductors, photodetectors, electrophotographic recording devices,capacitors, charge injection layers, Schottky diodes, planarisinglayers, antistatic films, conducting substrates, conducting patterns,photoconductors, electrophotographic applications, electrophotographicrecording, organic memory devices, biosensors, biochips, optoelectronicdevices requiring similar phase shift at multiple wavelengths, combinedCD/DVD/HD-DVD/Blu-Rays, reading, writing re-writing data storagesystems, or cameras.
 13. Optical component according to claim 11,characterized in that it is an optically uniaxial film selected from anA-plate, C-plate, negative C-plate or O-plate, a twisted opticalretarder, a twisted quarter wave foil (QWF), an optically biaxial film,an achromatic retarder, an achromatic QWF or half wave foil (HWF), afilm having a cholesteric, smectic, nematic or blue phase, a film havinghomeotropic, splayed, tilted, planar or blue-phase alignment, which isuniformly oriented or exhibits a pattern of different orientations. 14.Optical component according to claim 11, characterized in that it is anoptical compensation film for viewing angle enhancement of LCD's, acomponent in a brightness enhancement films, or an achromatic element inreflective or transflective LCD's.
 15. Method for preparing a compoundaccording to claim 1, comprising the steps of a) reacting a suitablysubstituted acetylene with an optionally substituted cyclohexanone inthe presence of butyllithium, b) separating the isomers thereby formed,c) esterification the tertiary alcohol of the isolated isomer of step b)with a suitable aromatic or aliphatic carboxylic acid, d) coupling theresulting compound via its axial acetylenic substituent to an aromaticring.